The water-rock interaction has a significant impact on reconstructing climatic and environmental changes using loess deposits. Lithium isotopes (delta Li-7) are important tracers to track this process. This study examined the Li contents and delta Li-7 values of different phases (water, weak acid leachate and residue were recorded as [Li](water), [Li](leachate), [Li](residue), delta Li-7(water), delta Li-7(leachate) and delta Li-7(residue)) within the upper 22 m Weinan loess-paleosol sediment located on the southeastern margin of the Chinese Loess Plateau. Significant variations were observed in both the [Li] and delta Li-7 values of different fractions within the loess. The water fraction samples have the lowest [Li](water) with less than 0.05 mu g/g. The leachate samples show relatively low [Li](leachate) levels ranging from 0.67 mu g/g to 2.45 mu g/g. In comparison, the residue samples exhibit higher [Li] values than the leachate samples, with the concentrations varying from approximately 29.45 mu g/g to 41.28 mu g/g. The delta Li-7(water) values are all higher than those of the corresponding leachate and residue, ranging from 14.7 parts per thousand to 28.2 parts per thousand. Additionally, the delta Li-7(water) values vary from -8.4 parts per thousand to 8.7 parts per thousand. The delta Li-7 of residue samples are relatively stable, ranging from -0.6 parts per thousand to 1.7 parts per thousand, with an average delta Li-7(residue) = 0.5 +/- 1.3 parts per thousand. The results indicate that the [Li](leachate) in Weinan Loess-paleosol sediments has excellent potential to indicate the variations of East East Asian summer monsoons during the last glacial-interglacial cycle, compared to the values of grain size, magnetic susceptibility, and CaCO3 content. Meanwhile, the delta Li-7(leachate) of loess not only can be utilized for tracing the pedogenic processes of weathering, eluviation, and migration, as well as for tracing groundwater impact. In the upper 15 m, the delta Li-7(leachate) can be employed to track soil water migration processes and the magnitude of pedogenic processes in loess at various time periods. Below the calcium carbonate accumulation layer (CAA, >15 m), there is groundwater, and CAA has impeded the flow of groundwater, making it difficult for the influence of groundwater to penetrate the CAA layer. Due to the prolonged exposure to capillary water, the acid-soluble phase lithium represents the lithium adsorbed by loess continuously absorbed from groundwater. delta Li-7(leachate) and delta Li-7(water) had basically reached equilibrium, with values of alpha ranging from 0.98 to 0.99 and an average value of alpha at 0.98. Our work thus shows that the delta Li-7(leachate) of loess-paleosol sediments may reflect equilibrium fractionation between sediments and groundwater, rather than pedogenic processes at the layer near groundwater.